In the related art, HE-AAC (High Efficiency MPEG (Moving Picture Experts Group) 4 AAC (Advanced Audio Coding)) (International Standard ISO/IEC14496-3) or AAC (MPEG2 AAC) (International Standard ISO/IEC13818-7) has been known as a method of encoding an audio signal.
For example, a method of outputting low frequency encoding information obtained by encoding a low frequency component and high frequency encoding information generated from a low frequency component and a high frequency component and used to obtain an estimation value of the high frequency component as codes obtained by encoding has been suggested as the method of encoding an audio signal (for example, refer to Patent Document 1). According to this method, information necessary to calculate the estimation value of the high frequency component, such as a scale factor to obtain a frequency component of a high frequency, an amplitude adjustment coefficient, and a spectrum residual error, is included in the high frequency encoding information.
In addition, when decoding is performed, the high frequency component is estimated on the basis of the low frequency component obtained by decoding the low frequency encoding information and information obtained by decoding the high frequency encoding information and the high frequency component obtained by the estimation and the low frequency component obtained by the decoding are synthesized and become an audio signal obtained by the decoding.
In this encoding method, because only the information to obtain the estimation value of the high frequency component is encoded as information regarding a signal component of a high frequency, encoding efficiency can be improved while an audio quality is suppressed from being deteriorated.